Method of controlling speed changes in hydraulically actuated type multiple-stage speed change gear

Abstract

A method of controlling speed changes in a hydraulically actuated type multiple-stage speed change gear, which renders it possible to prevent the occurrence of "shift hunting" without impairing the acceleration characteristics of the vehicle and also reduce the magnitude of shocks which occur at the time of speed changes even in case hydraulic clutches of small capacity are used. According to this method of controlling speed changes, a controller (30) is used to conduct speed changes when conditions for speed changes, i.e., upshift/downshift are satisfied, and in cases where a downshift is made after an upshift and an upshift is made after a downshift, speed changes are conducted after the lapse of a long speed change inhibiting time, and in other cases than the aforementioned, speed changes are conducted after the lapse of a short speed change inhibiting time. Further, only in case the vehicle is decelerated from a high speed stage to a coasting speed, deceleration operations are conducted with a direct coupled clutch (8) of the torque converter (3) kept in engaged condition, and in other cases than the aforementioned, speed changes are conducted with the direct coupled clutch kept in released condition.

What is claimed is: 
     
       1. A method of controlling speed ratio changes in hydraulically actuated type multiple-stage speed ratio change gear, arranged for conducting speed ratio change operations when conditions for speed ratio changes in the form of upshifts and downshifts are met, comprising the steps of: determining when a first shifting condition occurs wherein a downshift is indicated by a controller just after an upshift has been made or an upshift is indicated by the controller just after a downshift has been made;   delaying speed ratio change operations until after the lapse of a relatively long first shift inhibiting time when said first shifting condition has occurred; and   delaying speed ratio change operations until after the lapse of a second shift inhibiting time which is shorter than said first shift inhibiting time, when a shifting condition other than said first shifting condition has occurred.   
     
     
       2. A method of controlling speed ratio changes in a hydraulically actuated type multiple-stage speed ratio changes in a hydraulically actuated type multiple-stage speed ratio change gear as claimed in claim 1, further comprising the steps of: determining when a second shifting condition occurs, said second shifting condition being when the vehicle is decelerated from such a high speed that the second change gear is in a high speed stage, to a coasting speed, wherein said hydraulically actuated type multiple-stage speed change gear is combined with a torque converter fitted with a direct coupled clutch;   conducting downshifting operations with the direct coupled clutch of the torque converter kept in an engaged condition when said second shifting condition occurs; and   conducting speed ratio change operations with the direct coupled clutch kept in a released condition in all cases where the second shifting condition does not occur.   
     
     
       3. A method of controlling speed ratio changes in a hydraulically actuated type multiple-stage speed ratio change gear as claimed in claim 1, further including the steps of: providing a controller which controls speed ratio changes in accordance with predetermined instructions and performs the sub-steps of:   providing a speed ratio change command based on signals input to said controller including a speed stage signal from a gear shifting lever, an engine speed signal from an engine revolution sensor from which vehicle speed is determined, an accelerator OFF signal from an acceleration sensor, a brake OFF signal from a brake pedal, a speed ratio change gear input revolution signal, an intermediate shaft revolution signal, and an output revolution signal;   determining when said first shifting condition occurs;   determining when said predetermined shifting conditions are met as required by the predetermined instructions;   outputting said speed change command after the lapse of said first shift inhibiting time when said first shifting condition occurs; and   outputting said speed change command after the lapse of said second inhibiting time when said first shifting condition does not occur.